Two Questions about AD6676

2) What is the ultimate BW limit? I played with the online "AD6676 Remote Test Tool" and with the following settings AD6676 can digitize more than 200 MHz of bandwitdh:

FIF=450 MHz

BW=160 MHz

BWL=BWU=30

Decimation Mode=Dec-by-12

With these settings, when I run a signal transfer function test I get Upper -3dB corner as 564 MHz and lower -3dB corner 342 MHz. Please see the attached plot. Hence it seems it is possible to digitize more than 200 MHz of BW with AD6676. Is it really so? Why did you limit the bandwidth at 160 MHz in the specifications?

2) The BW at this high IF frequency is mostly constrained by the digital decimation filter BW. Table 14 of the datasheet shows the usable normalized complex BW vs decimation factor. For the widest bandwidth, one would operate with the lowest decimation factor of 12. For 60 dB stopband rejection, the usable BW is 0.617*FDATA_IQ.

2) The BW at this high IF frequency is mostly constrained by the digital decimation filter BW. Table 14 of the datasheet shows the usable normalized complex BW vs decimation factor. For the widest bandwidth, one would operate with the lowest decimation factor of 12. For 60 dB stopband rejection, the usable BW is 0.617*FDATA_IQ.

Thanks you for answering my question. The closest spurs are located at an offset FDATA_IQ - BW from the passband edges. In case of IF=450 MHz, BW=160 MHz, and Dec-by-12, the location of closest offset that causes an inband spur is IF+ BW/2 +(FDATA_IQ-BW)= 450+80+ (266.67-160)=636.67 MHz on the upper side. On the lower side it is 263.33 MHz. For 450 MHz IF and 160 MHz BW, the IF filter needs to supress 263.33 and 636.67 MHz about 30 dB. I got 30 dB value from the remote test tool. See the plots below:

On the other hand, for 200 MHz BW, the IF filter requirement becomes much more difficult. It needs to supress 283.33 and 616.67 by about 60 dB to bury the closes spurs into the noise floor. See the plots here:

So, it is possible to get 200 MHz BW out of AD6676, but it will require a very sharp filter (almost a SAW!).